This project, as well as project number Z01-CP-04852-02-LVC, studies the biochemical and biophysical properties of nucleic acids and polypeptides of mammalian leukemia and sarcoma viruses. Our major findings for this fiscal year are as follows: 1. Poly(C)- and poly(G)-rich sequences are present in the RNA of leukemia and sarcoma viruses from avian, murine, feline, and primate isolates. 2. Little or no poly(C)- and poly(g)-rich sequences are present in the messenger RNA examined from normal mammalian cells. 3. Genomic and subunit RNA of mammalian leukemia and sarcoma viruses have regions of double-stranded RNA. 4. Gazdar murine sarcoma virus (Gz-MSV) and Moloney murine sarcoma virus (M-MSV) are closely related and possibly Gz-MSV is a variant of M-MSV as determined by nucleic acid hybridization studies and analysis of viral expression in cells. 5. These studies represent a possible molecular approach to cancer therapy for some types of viral neoplasia. BIBLIOGRAPHIC REFERENCE: Phillips, L. A. and Pang, R. H. L.: The detection and characterization of polynucleotide sequences in the RNA of mammalian oncornaviruses. In Clemmesen J. and Yohn, D. S. (Eds.): Bibliotheca Haematologica No. 43. Basel, Switzerland, S. Karger AG, 1976, pp. 460-464.